"Climbing trees can be a fairly precarious exercise, but it's really important for children to learn how far they can go without hurting themselves, and experiencing that sense of adventure and risk-taking without always being stopped," she said.

"They're exploring social relationships, they're exploring the physical world, and if you deny them that you're denying them a really very important experience."

However, Australian Principals' Association president Norm Hart says most schools have got the balance right.

"We certainly don't want to bubble-wrapped children as a result of all this but by the same token, as a parent, if my kid comes home with a broken arm, I want to know that that was an accident that couldn't have been prevented," he said.

A spokesperson for the New South Wales Department of Education says it is up to principals to develop appropriate rules for their school yards.